Radioactive silver and cadmium bath composition and barrel plater therefor



Nov. 1, 1966 F. PEA STEI 3,282,854

SILVER AND BM TH MPOSITION RADIOACTIVE AND BARREL PLATER EREFO Filed May 6, 1965 INVENTOR.

FRED PEARLSTEIN ATTOR NEYS United States Patent RADIOACTIVE SILVER AND CADMIUM BATH COMPOSITION AND B A R R E L PLATER THEREFGR Fred Pearlstein, Philadelphia, Pa., assignor to the United States of America as represented by the Secretary of the Army Filed May 6, 1965, Ser. No. 457,245 3 Claims. (Cl. 252-3011) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty there- This invention is a continuation-in-part of my copending patent application, Serial Number 207,131, filed July 2, 1962 now abandoned, entitled Radioactive Silver and Cadmium Bath Composition and Barrel Plater Therefor and assigned to the same assignee hereof.

This invention relates to a new and useful radioactive composition. More particularly it concerns such a composition and a barrel plater cooperating therewith which permits copper or copper plated articles to receive a radioactive silver deposit and an overlying electrodeposit of cadmium wherein the article need not be transferred to dilferent solutions.

The presence of the critical shear pin in cartridge actuated devices cannot be detected by presently used nondestructive 220 peak kilovolts fluoroscopic inspection methods because of dense materials necessarily surrounding the pin. Similar situations arise, for example, in catapults, thrusters and other ordnance materials. It is well known that radiation from radioactive tracers can be used as a marker for determining the presence or absence of various parts or the position of a contact switch in an assembled item, such as the arming mechanism of an electronic fuze. Of the several radioactive substances, and particularly the gamma emitters, silver- 110 was found most suitable for tagging shear pins. This isotope has the following advantages: (a) formation of a uniform and adherent coating on the copper pins by simple chemical displacement, (b) no interference with the subsequent electrodeposition of cadmium on the radioactive silver, (c) emission of gamma radiation of suflicient intensity to permit thickness of metal up to 1 inch or more, and (d) a half-life of about 270 days such that the pins can be prepared several months in advance, yet the activity used will be reduced to the background of the measuring instrument in from 2 to 3 years.

In order to prevent accidental rub-01f of the silver-110 from the shear pins during handling, assembly, and the like, and to increase its corrosion resistance, an overlying protective metal such as cadmium is electrodeposited over the silver which heretofore required a separate solution or solutions necessitating the transfer of the radioactively treated pins thereto.

Briefly then, my invention overcomes these problems by providing a single solution which permits both an immersion deposition of the silver and an overlying cadmium electrodeposit without the necessity of transferring the pins when such a solution is used with my novel barrel plating apparatus.

Accordingly, it is a broad object of this invention to provide means for applying a radioactive silver deposit and an overlying cadmium electro-deposit to copper or copper plated components.

Another object of the invention is to provide a solution which will permit copper shear pins to be immersion deposited with radioactive silver and an overlying electrodeposit of cadmium without requiring additional pin transfer.

A further object of the invention is to provide a simple ice processing container for accomplishing the foregoing objects.

Other and further objects of the invention will be apparent to those skilled in the art upon study of this disclosure and the single drawing illustrating a vertical section of my barrel plating device which is used in conjunction with the solution or bath composition of my invention.

Referring now to the drawings, there is shown a barrel plating device at 10 and having a cylindrical body portion 12 made of an electrical-nonconducting material which is preferably somewhat transparent, such as Plexiglas, for example. A disc 14 of like material is fitted about the lower open end of body 12 in water-tight relation thereto and a stainless steel cathode 16 of a similar shape is adhered thereon. A stainless steel anode 18 in the form of an annulus is fitted within an upper portion of body 12. Insulated electrical conductors 20 and 22 are connected to the anode and cathode respectively and are led generally downwardly into a hollow shaft 24 through orifices 26 and 28 provided therein to spaced conductor rings 30 and 32 respectively, the rings being electrically insulated from the shaft wall as indicated at 34. Conductor 22, leading from cathode 16, passes through opening 36 provided in disc member 14 and finally through another opening 38 in conductor ring 30. The shaft itself will be suitably screw-threadedly mounted to the disc 14. Contacting the conductor rings are a pair of spring-loaded brushes 30' and 32 which are connected to a direct current power source such as a battery 42, through a switch 44, the polarity of the battery being indicated as shown. The barrel may be supported in any convenient fashion such that its angle of operation may be controlled, or to permit dumping. of its contents, by being rotatably, as shown schematically simplified, around pivot pin 46. It will also be understood that although the drawing shows a single electrical contact to each electrode, it may be desirable to employ a plurality of such connections to each electrode.

' Several shear pins 50 are shown immersed in my novel solution 52 to be hereinafter described.

Finally, a bafile 54, preferably of like material as body 12 but optionally of any durable plastic material, in the shape of a rod, for example, is secured to the body and functions to aid in the tumbling of the shear pins.

Since the same barrel is employed to contain the solution providing the underlying radioactive silver deposit and the cadmium electrodeposit, the material comprising the electrodes must remain insoluble during electrodeposition as well as be incapable of picking up substantial quantities of the radioactive silver. I have found that stainless steel, and more particularly 18-8 stainless steel, works admirably well to meet both requirements.

My radioactive silver-cadmium bath composition 52 consists essentially of about 20 g. CdO, about 120 g. NaCN, about 5 g. NaOH, about 10 g. Na CO the balance being water to substantially make one liter. To a suitable quantity of this solution, it has been found to work admirably well if sufiicient Agis added thereto such that each pin treated in a batch will be marked with approximately 0.02 microcuries Ag-llO, the shear pin being of normal dimensions of about inch diameter and about inch long.

Ag-ll0 is an isotope of silver and will be introduced into my bath composition preferably in the form of a salt, such for example as Ag NO Each liter of the above solution will normally treat about 350 of the aforementioned shear pins, each marked with approximately 0.02 microcuries Ag-l10. The required 7 microcuries (350 .02) of Ag-llO is conveniently added to the above solution from a stock solution containing one microcurie Ag-llO (2X g. Ag-llO) The Ag-l10 is present in the stock solution as I per ml.

Ag NO However, if it is desired to tag the pins with I a greater or lesser radioactive level, the Ag110 added will be proportionally varied and will conveniently range between 3 to 15 microcuries Ag-llO in the above example, butis not limited thereto.

Of course, it will be understood that the Ag N0 $011k tion also contains non-radioactive silver due to decay. Therefore, the total silver content should be below about 10* gms./liter for the above example in 'order'to insure substantially complete immersion deposition of the silver.

'In operating my device, the articles to be treated are The solution, without the introduced into the barrel. Ag-llO, is poured carefully into the barrel and the leadshielded Ag NO then cautiously dispensed thereinto. The barrel, without the application of 'electrodepositing current, may now be rotated for about minutes at 20 to r.p.m., the barrel being inclined about to degrees from the horizontal. Within the neighborhood of 20 minutes, about of the radioactivity of the solution is transferred tothe copper shear pins or articles to be treated. Switch 44 is then closed 'such'that the electrodeposition of cadmium on the Agsurface is effected, and requiring about 5 to 25 amps/ft. of pin surface and about 10 to 15 minutes or until'about 0.0002 inch deposit is obtained. I have found that excellent deposits-are obtained when the entire operation is carried out at ordinary room temperature. The contents of the barrel may now be dumped onto a screen and the liquid ,drainedas with other chemicals, the disposal problem being virtuallyeliminated since the ;e'lectrodeposition of cadmium will transfer the majority of the remaining 10% radioactivity onto the shear pins. The pins may now be washed and dried. Any cadmium'deposited' on the stainless steel electrodes may easily be removed by a solutionvof ammonium nitrate in the proportion of about 1 pound per gallon of water and thus preventing any radioactive silver from depositing upon the cadmium in succeeding runs.

Considering the extremely high free cyanide to silver ratio in my solution, it would have been totally unexpected to one skilled in the art that silver would immersion deposit on copper from this solution. Because I most metals to be plated with silver will precipitate by immersion from the regular'silver plating bath and result in poorly adherent deposits, the best practice includes first striking in a solution of very much lower silver content and'high free cyanide content, such as'exemplified by the following conventional silver striking bath which prevents silver from being immersion deposited:

Silver cyanide0.5-O.7 oz./ gal.

Potassium cyanidel0*12 oz./ gal.

My composition, having yet a-tremendously higher ratio of free cyanide to silver, does not prevent silver from immersion depositing, but yet does provide copperarticles I with a layer of sub-:monoatomiethickness, with excellent immersion deposition of silver.

I claim:

1. A bath composition for both immersion'depositing.

radioactive silver on copper and copper plated articles and electrodepositing an overlying cadmium layer thereon,

said composition consisting'essentially of about 20 g. CdO,

about g. NaCN, about 5 g. NaOH, about 10 g.

Na CO about 3 to 15 -microcuries Ag-1l0 added thereto in the form of Ag NO ,;an'cl the balance being water to make one liter.

, 2. The composition of claim. 1 further characterized by being capable of immersion depositing between about .01

to .04 microcurie of Ag-llO on each'of about 350 of said articles, each of said articles being about inch in diameter and about inch long.

3. The composition of claim 1 further characterized by being capable of immersion depositing about .02 microcurie of Ag-ll0 on each of about 350 of said articles, said composition containing about 7 microcuries Ag110, each of said articles being about 1 inch in diameter and about inch long. I I I I I References Cited by the Examiner International Journal of Applied Radiation and Isotopes, vols. 5-6, No. l, 1959, pp. 51-56.

BENJAMIN R. PADGETI, Primary Examiner. S. I. LECHERT, Assistant Examiner. 

1. A BATH COMPOSITION FOR BOTH IMMERSION DEPOSITING RADIOACTIVE SILVER ON COPPER AND COPPER PLATED ARTICLES AND ELECTRODEPOSITING AN OVERLYIN CADMIUM LAYER THEREON, SAID COMPOSITION CONSISTING ESSENTIALLY OF ABOUT 20 G. CDO, ABOUT 120 G. NACN, ABOUT 5 G. NAOH, ABOUT 10 G. NA2CO3, ABOUT 3 TO 15 MICROCURIES AG-110 ADDED THERETO 